Insulated electric conductor



Aug. 7, 1945. A. o. RYAN INSULATED ELECTRIC CONDUCTOR Filed Nov. 5, 1942IN VEN TOR. ,4L BERT 0. /PVq/V B Patented 7, 1945 UNITED STATESi-'fii'iiazirry oF-Fici-z V wise: l

INSULATID me AIJNDUI'`)I alumni-.1.,

assigner to Corporation, New

York. N. Y.. a corporation olDeiaware Ammann Nambe s, im, 'serai N. am

- s claims; ici. 11i-es) This invention relates to insulated electric oonductor and more particularly to electrical lines o! theconcentrioconductor type.

The object is to provide an insulation covering laround a conductorcontaining a substantial proportion of air to solid and over which asheath.

ing such as an outenconductor may be directly applied. lation containingair which will support without derormation or sanina' an outer sheathingor conductor which is not self-supporting A related object is to provideaninsucroise' section; and

nisweu knownimisimofiensniniidinableinsulationordielectriearoundanelectrleal' conductor and between thecentral and outer eonduetorsoiaconcsntricline. Touseairaroimdacentralconductoritisrequiredto'space.theoutersheathingorconductorby'somesolid spaclngmeans';anditisdesiredtoprovldeas highaspracticalaratiootairtosolid. Manyexpediente have been propoeedtor 'doing this, auch as wrapvim cords inloose helices around the central conductor, placing insulating beadsolglassorthelikeovertheconductorgandeimiiar spacing element and theouter smooth suriaceot such insuiatin! as a support tor the metal braidor conducuse oi such an auxiliary insulating tubwihepmporuonofmusmsinndmFig. 1 illustrates a conductor having an airniied tubingofinsulationwrapped around it;

HLIGisacroIssectiontakenat of ll'igfl;

outer conductor sheathing tiahtlr wrapped around it, the other'sheathing being shown in Pig. 2a shows a' cross sectional view takenline 2a-2aotl"ia.2.

H8. 1 shows a conductor strandedorasolidwirewithawrapmotan alr-lledlnlilllMDl tubinl Il. The tllbllll' il hollow as shown in Fig. lo andpreferably cyiin-r.

. drical asshown. and itis wound inahelix aroundtheconductorinacloeelaysothatadiaoentturns toucheach'other.Ilitisdesiredtoincreasethe lvpitchoithehelintwoorthreeormxeotthe '0.would ordinarily be obtained. however. when it The invention is.carried out by wranlllna an air nlled tubing around the centralconductor -anni placing the outer sheathing' or conductortirhtlyoverthetubingtoholdthetublnzina substantlallyornearlyrectanguiarorsquarecross section The invention will be, more fullyunderstood from the toil wing detailed descripion with the drawing tubesmay be wound together. side by side. Reiiardless. of the number oi'tubes or helices used. the adjacent tubes, should be made substantiallyto touch each other; and this is what is meant by the term close lay" asused in this specifica- 'Ihere is wrapped over the tubular lay'il. enyThil Il.

outersheathing il (Figs. 2 and 2a). ordinarily and preferably an outerconductor although it could be, i! desired, an insulation tubing. Thegreatest advantage oi the invention is ,aconducton forming with theinner conductoi'l il a concentric line. The outer conductorwiiibemouewtheiseiinsttnesaisntwm or substantially touch 'each other.This niaybedonebythe applicationof the prOPr byabraldingmaehineinawelikncwn ,bywhichabraidoicopperorotherreasonoithecrosssectionshown-inl'iulland "et 3s,- adJaoent walls o!adjacent turns eontacteach 'rms immane unam-m warum the innerand outerconductors is oi primeimporlltanoeinaconoentrlelineastheeleotrloalcharline Iaia m. 2 snows theconductora: il'ig.r i with sn il. which may be tudmauy through scribedas phenanthrene,

degree of flexibility and a low dielectric constant and preferably lowpower factor. It should preterably be sufiiciently yielding and elasticto assume the substantially square or rectangular cross section and holdthat shape against the pressure from the outer conductor. The greaterthe pitch of the winding of the tubing, as when a plurality of tubesare.used side by side, the more elongated the rectangular sectionbecomes. as taken longicable. It will be understood that thesubstantially square cross section shown'in'PigaZandMisinfactarectangularcroes section of which all sides aresubstantially equal. Polyethylene meets these requirements and issuggested as a preferred material as it has the desired electrical andinsulating properties. There could also be used polystyrene plasdcisedwith a suitable plasticiser for example, as described in tbe UnitedStates Letters Patent 2,272,996. \Buitable plasticisers are theredeisoamylnaphthalene, c-propyinaphthalene', pmethyinaphthalene,iluorene, p-naphtbylmethylether, -naphthylethylether.octahydroanthracene, and octahydrophenanthrene. Rubber or 'rnc tubingil. should preferably be, no may rubber-like materials could also beused, and also mixtures of polystyrene 1 for an outer conductorVisuzsefulincsiiseswherea 2 aseaooaaoteristicsoftheiineareaiiectedbytbespaoing. sion.Itmaybedesirableinmsnycasestoseal Intheabsencecfthepexipheralsupportinlmroifthetubingatintervals. faceunifcrrmlyspacedtromthecenh-alconduc-.Thecrosssectionoitbetubingneednotalwan Atonthernietalbraid sheathing,notbeing selfberectangularasillustratsiinl'igs.2and2s.but supporting.wouldsag in places. with consequent s might depart considerably fromthis shape. so deleterious results. A l long as the adjacent tubes arein direct contact The material of the tube or tubes Il should be witheach other. an insulating material having a reasonably high By the useof this invention it is possible to.A

Vobtain an insulated or concentric conductor in which the insulationyhan a relatively high proportion of air to solid, thereby aording theadvantages of an air dielectric; and the insulation at the same time isrigid and iixed enoughin place to hold the outer sheathing rigidly inpl'aoc and without deforming, and it furnishes a base such as a braidwithout displacing. Hy cable low capacity lcable u wanted, for examplewhere high frequencies are what is claimed iszf 1. An insulatedconductor comprising a central conductor and hollow airl iilled tubularinsulating means wrapped around the central conductor in a close lay anda sheathing fitted tightly around the tubular lay, the turns of saidtubular lalhav permittms my Silm 0l' ing. a substantially square orrectangular ercm section and lying against each other and forming arigid support for the sheathing.

2. A concentric electrical line comprising a centrai conductor,' anair-filled tubular deformable and exible insulating material of normallycy- N-lindrical cross section wrapped around the conducto'r in a closslay and an outer conductor sheathing wrapped tightly around the lay witha tension which deforms the turns cf the tubular material from the.cylindrical cross section.

a. A une according to claim 2. in which the tu-' bular means is sealedoif to hold-tbe air within it and prevent collapse.

, 4. A line according to claim 2 in which the sheathing is supported bythesaid insulating material wrappedaround the conductor.

5. The method of making a concentric line u which comprises wrapping adeformable air-diled needbeinsomecaseasealedoiittosealtheair.

within it. o um it wm not comme when tho outer sheathing i2 is beingapplied under tenhollow tubular member in a clcse`he1ix around theconductor, sealingthe air within the tubular member and placing auoutersheath around the .o tubular member under tension.

